The women were indicted Thursday on two counts of attempted first-degree murder for stabbing and wounding Avery's older children, a 5-year-old girl and an 8-year-old boy, said Montgomery County, Md. authorities.

Avery and Sanford told investigators that they believed evil spirits jumped between the bodies of the children and that they needed to perform an exorcism to drive the demons out, said Montgomery County State's Attorney John McCarthy.

When being questioned by police, the women told investigators that they tried multiple methods to remove the presence of demons from the children, progressing from attempting to break the neck of the youngest child, to strangulation, to stabbing.

A neighbor called 911 after seeing a car with an open door and a knife that appeared to have blood on it. The timing of that 911 call likely helped saved the lives of the older children, police said.

Prosecutors say the women left the bodies of Norell Harris, 1, and Zyana Harris, 2, on a bed. The older children were found with stab wounds.

Authorities said Sanford had recently moved into the townhouse where Avery had been living with the four children. The women identified themselves to investigators as members of a group known as the "demon assassins."

Avery described herself as the commander and Sanford her sergeant.

Edward Leyden, a lawyer for Sanford, told reporters after a hearing in January that "everyone who is involved in this case is in deep pain."

The family has ties to Philadelphia. After the women's arrest, NBC10 spoke with an uncle of the victims who did not want to comment on the attack. The children's grandmother is also from the city.